A mobile radio is known is disclosed in Japanese Patent Publication (Kokai), No. 2003-309473, which is configured to keep its housing temperature from rising. In the publication, a technique is shown for keeping housing temperature from rising in the above publication, by limiting a period of time of consecutive transmission to a value t1 and banning the transmission for a certain period of time after the housing temperature reaches t1.
As shown in “Embodiment of the Invention” of the above publication, the mobile radio has a temperature sensor, and sets its transmitter power to a normal value before t1 and reduces the power after t1 if the temperature is no higher than a threshold. The mobile radio bans the transmission if the temperature exceeds the threshold. By this operation, the mobile radio may reduce a period of time while the transmission is banned and may improve capability of emergency calls.
An image photographing device is disclosed in Japanese Patent Publication (Kokai), No. 2001-257912, which is configured to extend battery endurance by saving power. According to the publication, the image photographing device may save power by reducing a number of pixels per a frame and by reducing a frame rate.
Owing to a trend of multi-functioning and downsizing in recent years, a mobile communication apparatus, e.g., a mobile phone, often suffers from thermal problems. One of the problems is a time limitation of a TV call during which a plurality of heat dissipating devices like a main camera, a sub camera and a radio amplifier works together to dissipate lots of heat.
The technique of the transmission time limitation described above has a problem that the period of time of consecutive transmission is limited to the value t1 and may not be extended over t1. The mobile radio described above has a problem that the temperature sensor is required and that a transmission performance may be degraded due to the power reduction after t1.
The image photographing device described above may contribute to power saving, but an effect to its temperature is unknown. In general, reducing the number of pixels or the frame rate may contribute to power saving, but may not be counted on to alleviate thermal problems.